Vehicles such as some lawn and garden tractors have power take offs (PTOs) that are used to drive implements such as mower blades. Prior lawn and garden tractors with PTOs have included interlock circuits that prevent engagement of the PTO driven implement when the vehicle is in reverse. Under certain conditions, operation of a PTO driven implement while the vehicle is in reverse is desirable. Various override systems have been proposed that allow operation of a PTO driven implement in reverse.
Override systems have been developed that use a momentary over-ride switch that latches an over-ride relay. The over-ride relay is unlatched when certain other conditions are met, like shifting out of reverse. One problem with override systems that rely on relays is that relays can stick in a closed state or the relay may not may not connect when energized. Use of multiple relays and implementing time delays can result in complex, expensive and difficult to service override systems.
One proposed system uses a four-position ignition switch (Off, Run with over-ride on, Run with over-ride off, and Start). In that system the user must turn the key to the start position to start the engine, thus resetting the over-ride on engine restart. The ignition switch spring returns the key from the Start position to the Run with over-ride off position, requiring an additional intentional movement of the key by the user to select Run with over-ride on option.
United States published application 2004-0201286 to Harvey et al. entitled “Reverse Operation Safety Circuit” concerns a safety system for a riding lawn mower that prevents powered operation of a PTO driven implement while the tractor is in reverse unless an override switch is “ON”. The override switch may be a sustained action two position switch and the PTO driven implement may be a lawn mower blade. In one embodiment, the override switch does not allow the engine to start if the override switch is on. In one embodiment, the override switch cooperates with an operator presence switch to prevent operation of the PTO driven implement when the override switch is on and the operator is not present. The disclosure of this published application to Harvey et al. is incorporated herein by reference.